Separation of materials by flotation



March 19, 1929. F ELMQRE 1,706,281

SEPARATION OF MATERIALS BY FLOTATION Filed April 23, 1927 WWW/6% Patented 1929.

ram EDWARD ELMORE, for BOXMOOR, ENGLAND.

SEPARATION OF MATERIALS BY FLdTATION.

application filed April 23, 1927, Serial No. 186,114, and in Great Britain July 16, 1926.

ish specification No. 29,282 of 1904) have a This invention relates to the separation of materials by flotation, more particularly to the cleaning of coal and the concentration of ores and the like (allsuch materials being 6 for brevity hereinafter termed mineral)- by flotation, and in particular relates to improvements in the vacuum process of flotation andt-lie apparatus used therein.

In thesaid vacuum process as heretofore loconducted the pulp of mineral and water has, after agitation with oil or similar agent, beensucked up through a pipe from a reservoir into the separating chamber by the vacuum maintained therein. The velocity of the'p'ulp in this pipe has generally been made such'as to insure that the heaviest mineral grains are carried up into the separating chamber. As the pulp rises in this pipe andapproaches the separating chamber, the

pressure on the ulp progressively decreases, thus causing a li eration of the dissolved and I contained gases and their expansion in the pulp. Such expansion leads to an increase in the volume of the pulp and a corresponding increase-in its velocity up the pipe.

By observation of what occurs in the pipe I have found that the considerably increased velocity thus produced leads to turbulence and a detachment of clean mineral grains from the bubbles of gas liberated by the decreased pressure, The mineral grains so de- 'tached are to a considerable extent lost in the residues. I

In some forms or apparatus ,(s'uch'as the apparatus described in British specification No. 191,383) the pulp is admitted in a horizontal or approximately horizontal direction into the separating chamber at such velocity as to cause rotation of the wholeof. the pulp 40 therein. By observing what occurs in suc apparatus I have found that the;rotation leads to the creation of eddying currents or turbulence-in the separating chamber and a loss of clean mineral by its detachment from gas bubbles; also that a' considerable loss of mineral also occurs in the horizontal-part I of the'inlet pipes, owing to the rubbing oi the bubbles laden with clean mineral along. the underside of the top of the pipe-,which' to causes detachment ofclean-mineral from the bubbles. The same effect is also produced by the bends in the pipe where it turns from the verticalto the'hor'izontal position.-

Mechanical rakes or stirring arms in the separating vessel (such as described inBriQ similar effect in detaching mineral grains from the bubbles. a

All these defects are particularly important in treating coarse particles. v

By the use of my improved vacuum process and apparatus these defects are largely overcome, and I am enabled, forexample,

successively to treat coal crushed to a larger sizcand with a larger through-put than hitherto.

water,-mineral and selective agent, such as oil, is sucked up into-a separating chamber as.

a substantially vertical stream,which is free stant velocity. In this manner turbulence is mini zedand'the bubbles and attached mineral rise quietly.

One mod-e of'obtaming the substantially constant velocity consists in arranging that According to the invention the pulp of I the stream shall have an increasing crosssection in the upward direction. The bubbles and attached mineral should be se arated from the stream in the separating c amber without aid of mechanical rakes or stirrer's.

enable a further portion of clean *mineralm grains to rise and be separated, any commu-' 'nication of rotary movement to the main body of flotation froth above being largely prevented by stationary baflles arranged around the point of entry into the separat ing chamber of the-non-turbulent stream of hpulp.

The inventionffurther consists in apparatus suitable for carrying out my-impro'ved process, said apparatus comprising a separating chamber having the usual conical or like contracted'upper part connected with a vacuum pump, an outlet pipe for the concentrates, and an outlet for the depleted pulp,

and said chamber also having a central substantially vertical suction-pipe for the pulp,

free from bend or horizontal portions and;

so tapered in ver ical section that-the rising pulp as it expands under the action of the falling pressure continues to ascend therein as a non-turbulent stream of approximately constant velocity.

The foregoing features of my invention and other features thereof will now be exthe upper part, and an outlet opening f at its lower part connected with a discharge pipe 9 extending downwards into a launder h'. Into this pipe there extends at a suitable point a downwardly directed jet 11 connected with a water supply. The end of pipe 9 is sealed under water or fitted with a non-return valve.

The open bottom of vessel a is "connected:

with a pipe 70 which extends downwards into the launder Z and is closed at its lower end by a valve'ma The stirrup n which carries this valve is connected with a lever 0 centered at p and connected at its other end by rod 1 with a, lever r centered at s and subject to the action of a rotating cam t.

A rising pipe it connected by a U-bend 'v with a pulp hopper w extends axially in the vessel a to about the junction of the vessel with its upper part b. This pipe expands up- 'wardly and its open upper end has a number of co-axial rings w forming circular louvres. From thisportion of 'the pipe extend radial baflies 3 2 is a jet extending more or-less tangentially into the vessel a and connected with a water supply. I a

The operation of the apparatus is as follows, it being assumed,'asan-example, that vided coal. L

The pulp (a mi 'ture of the material under the material under treatment is finely subditreatnient, water and one of the known selective agents, for instance oil), after having been stirred or agitated as is well understood, is fed into the hopper w and the vacuum pump connected with pipe e is put in action. The pulp is sucked up the pipeu and fills'the vessel a b and the pipe 70. Y The ,cam 25 is set in rotation to open periodi'callythe valve m. the

extent of such opening being adjusted by means of a turnbuckle 9'. The bubbles of. gas

liberated from the water in the pulp which is rising up the pipe u, as well as the gasadsorbed on or in the coal particles, attach themselves to the particles of coal in prefererine to the particles of mineral matter forming a part of the ash. As the bubbles ascend the pipe they grow in size and'there i'sjiitendency for the volume of the pulp to increase, accompanied by a corresponding increase in its velocity up the pipe. This latter tendency is counteracted by the increasing diameter of the pipe, so that the pulp rises in the latter as a stream having'approximatelyconstant velocity and without turbulence. Since there are no bends or turns in the pipe la there is little tendency for the particles which are buoyed up by attached bubbles to become detached from the bubbles by friction against surfaces.

As the rising pulp leaves the tube u. the heavier particles of ash-material which have no bubbles attached to them and begin to descend againstthe stream, escape through the openings between the rings m and pass into vessel (/1. \Vere such particles allowed to continue to descend within the pipe u theymight cause. particles of coal to become detached from their gas bubbles. I

The particles of coal carried by the adher- 'ing bubbles continue to rise in the upper part b of the vessel and finally pass through the throat 0 into the receiver d which they leave by the pipe 9. I

In treating some pulps a voluminous froth is produced which is discharged too slowly by the pipe 9, the through-put of the machine being thus reduced. 'To overcome this objection means may be adopted for reducing the pressure in this pipe and increasing the velocity therein, the means here shown being the ejector jet 5 supplied with water under pressure. 3 j

The ash constituents collect in the vessel a and descend the pipe is ultimately escaping past valve Z as this is periodicallyopcned by action of cam 25 on lever 7'. This opening and closing of the valve produces a pulsation of .the contents of the vessel a b which prevents clogging of the-coal in the upper part b and the formation ofchannels therein. Such channelswould allow the water alone to flo'w away without any coal passing down the P P? 9- Since some particles of coal having adhering bubbles find their way together with the ash constituents into the vessel a, it is advantageous to impart to the contents of this vessel a rotary movement to aid the ascent of the coal particles unimpeded by the descent-of the ash constituents. Forthi's'purpose Water under pressure is admitted into the vessel a through the aforesaid tangentially directed jet 2. In ordenthat the rotary movement may be communicated as little as possible to the contents of the upper part b, bafiie plates 3 extend'radially from the mouth of the pipe u to the periphery of part I).

'Having now particularly described and ascertained the ,nature'of my said invention and the best means I know of'carrying the same into practice, I claim 1. Ayacuum process of separating materials by flotation which process comprises agitating the material with 'water'and a selective agent to produce a pulp containing elastic fluid causing the pulp to ascend under a reduced pressure as a substantially vertical stream free from changes of direction and travelling at approximately constant veloc-- lllO ' scend.

ity into a body of liquid wherein selected particles of the material ascend while others de- 12. A vacuum process of separating materials by flotation which process comprises agitating the material with water and a selective agent to producea pulp containing elastic fluid, causing the pulp to ascend under a reduced pressure as a substantially vertical stream having an increasing cross section in the upward direction compensating for increase in volume of the ascending pulp due to expansion of elastic fluid contained therein so'- that the ascending pulp travels at approximately onstant velocity and causing the n stream ascending pulp ,to entera body of liquid wherein selected particles ascend while others descend. t

3. A vacuum process of separating mate rials by flotation wh ch process comprlses agitatmg the material with water and a selective-agent'to produce a pulp containing elastic fluid, causing the pulp to ascend under a reduced pressure as a substantially vertical stream free from changes of direction andtravelling at approximately constant velocity into a body of liquid wherein the clean mineral particles ascend while the depleted pulp descends and imparting rotary movement about a' substantially vertical axis to that part of the body oi liquid in which the depleted pulp is descending. Y

4:. A vacuum process of separating materials by flotation which process comprises agitating the material with water anda selective agent to produce a pulp containing elastic fluid, causing the pulp to ascend under a reduced pressure asa substantially vertical stream having an increasing cross section in the upward direction compensating for increasenn volume of the ascending pulp due to expansion of elastic fluid contained therein so that the ascending pulp such that it travels at approximately constant velocity causing the stream of ascending pulp to enter a body'of liquid wherein the clean mineral particles ascend while the depleted pulp descends and imparting rotary movement about a substantially vertical ardis to that part of the body of liquid in which the depletedpulp is descending.

5i Apparatus for a vacuum process of separating materials in a pulp by flotation, comprising a separating vessel,-a substantially vertical suction pipe having an increasing cross-section in the upward direction and extending upwardly into the said vessel, and means for suckingpulp up the said pipeinto the said vessel.

'6. Apparatus fora vacuum process of separating materials in a pulp by flotation, comprising a separating vessel, a substantiallyvertical suction-pipe having an increasing cross-section in the upward direction and extending "upwardly and co-axially into the said vessel to a lev l about the'middle. ofth e .height thereof, and means for sucking pulp.

up the said pipe into the said vessel.

7. Apparatus for a vacuum process of separating. materials in a pulp by flotation, comprising a separating vessel, a substantially vertical suction pipe having an increasing cross-section in the upward direction and extending upwardly and co-axially into the said vessel to a level about the middle of the height thereof, at least one ring of larger diamcter than the pipe forming'a Circular 1011-. vre opening in the upper part of the pipe,

and means for sucking pulp up the said pipe into the said vessel.

.8. Apparatus for a vacuum process of separating materials in a pulp by flotation; comprising a separating vessel, a substantially vertical suction pipe having an increasing cross-section in the upward direction and extending upwardly and co-axially into the said vessel to a level-about the middle of the height thereof, a number of co-axial rings ofsuccessively larger diameter than the pipe arranged to form circular louvre openings at the upper: part of the pipe and means for sucking pulp up the said pipe into the said vessel.

9. Apparatus for a vacuum process of separating materials in a pulp by flotation," comprising a separating vessel, a substantially vertical suction pipe having an increasing cross-section in the upward direction and extending upwardly into the said vessel, at

least one j etarranged to deliver Water under pressure .in substantially tangential direction into the said vessel at a part thereof which is below the level of the upper end of said'vertical suction pipe, so as to impart a rotary motion to liquid in the part of the vessel below said level and means for sucking pulp up the to deliver water under pressure in substane tially tangential direction into the part of the said vessel below the said baflle plates so as to impart a rotarymotion to liquid in the part of thevessel belowsaid battle plates and means for; sucking pulp up the said pipe into the said vessel. I

11. Apparatus for a Vacuum? process of separating materials in a pulp by flotation,

comprising a separating vessel, a conical upper part to this vesseha delivery throat at the summit of the conical part, a receiver surrounding the said throat and adapted to be connected with a vacuum pump, a discharge pipe connected with the receiver,'an ejector in this discharge pipe, a substantially vertical suction pipe having an increasing cross-section in the upward direction and extending upwardly and co-axially into the said separating vessel, and'a' discharge pipe connected With the.said separating vessel.

'12. Apparatus for a vacuum process of separating materials in a pulp by a fiota tion, comprising a separating vessel, a conical upper part to this vessel, a delivery throat at the summit of the conical part, a receiver surrounding the said throat and adapted to be name to this specification.

connected With a vacuum pump, a discharge suction pipe having an increasing cross-section in the upward direction-and extending upwardly and co-axially into the said separating vessel, a discharge pipe connected with the said separating vessel, a valve closing the lower end of the last-named discharge pipe and means for periodically opening and closing the said valve.

In testimony whereof I have signed my FRANK EDWARD ELMORE. as 

